Solder coating devices are known in which melted solder from a liquid solder bath is pumped to and delivered from a nozzle and coats the surface of a workpiece in the proximity of the nozzle. With this type of coating process, the molten solder is easily oxidized and presents problems when the solder oxide is returned to the solder bath. The oxidation of the solder is due to at least two factors: the sprayed solder is exposed to the atmosphere during the coating of the workpiece and the fall of solder droplets back into the solder bath, and the surface of the liquid solder bath is agitated by the returning solder droplets which aids in the oxidation of the solder bath.
To aid in the control of oxidation of the solder bath, oxidation preventive agents are generally added thereto. However, these oxidation preventive agents have problems in that they deteriorate from the heat of the solder bath over the course of time and thereby lose their effectiveness, and they tend to deposit on the surfaces of the solder coating device and thereby hinder the application of an uncontaminated coating to a work-piece. Additionally, the replenishment of used solder and oxidation preventive agents requires the shutting down of the coating device and thereby is expensive and time consuming.
On the other hand, if oxidation preventive agents are not added to the solder bath, solder oxides tend to build up around the mouth of the solder nozzle and thereby hinder the flow of solder material therefrom. Accordingly, the application of an even coating to the workpiece is made more difficult.
It is, therefore, a primary object of the present invention to provide a solder coating device which uses a spray nozzle and does not require the addition of an oxidation preventive agent.
It is a further object of the present invention to provide a solder coating device which enables the removal of solder oxides from the solder bath without the shutting down of the coating device.
It is a still further object of the present invention to reduce the formation of solder oxides in a solder bath for a solder coating device by preventing the direct re-entry of solder delivered from a nozzle into the solder bath.
It is another object of the present invention to prevent the formation of solder oxides in a solder bath used in the coating of a workpiece by a spray nozzle by conducting the coating process in an inert atmosphere.